[test] Fix 'argument must be str, not bytes' for Python 3.
[test] Fix 'argument must be str, not bytes' for Python 3.

Use `sys.stdout.buffer` instead of `sys.stdout` in lldbpexpect.py.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@370545 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb